(1) Field of the Invention
The present invention relates to a method for degrading volatile halogenated aliphatic hydrocarbons containing 1 to 3 carbon atoms without producing toxic residues from the degradation. In particular the present invention relates to the use of Pseudomonas fluorescens NRRL-B-18296 combined with a carbon source so that halogenated aliphatic hydrocarbon is degraded to non-toxic products (carbon dioxide, water and hydrochloric acid).
(2) Prior Art
Volatile haloaliphatic hydrocarbons are a major source of contamination in underground aquifers since they migrate readily. Most of the hazardous halogenated aliphatic compounds released from industrial, commercial and agricultural sources are chlorinated alkanes and alkenes which contain between one and three carbon atoms. These halogenated aliphatic compounds are exclusively products of human activities and are not produced by nature. The extensive use of these compounds in industrial processes has created a substantial problem in the disposal of waste material and a pollution problem.
The aerobic metabolism of trichloroethylene by Acinetobacter sp. has been reported by Nelson et al (Nelson, M. J., et al., Appl. Environ. Microbiol. 52:383-384 (1986)). This particular bacterium is induced to degrade trichloroethylene through prior growth on phenol (Nelson, M. J., et al., Appl. Environ. Microbiol. 53:949-954 (1987); however this method would be difficult to use in environmental applications since phenol is also a toxic substance. The ability of Xanthobacter autotrophicus to metabolize 1,2-dichloroethane and 2-chloroethanol has also been reported (Strotmann, U., et al., Curr. Microbiol. 15:159-163 (1987)).
The volatile haloaliphatic hydrocarbons are resistant to biodegradation in the aerobic subsurface environments such as aquifers, which contributes to their persistence in ground water. Certain anaerobic acetate degrading methanogens are capable of transforming short chained haloaliphatic hydrocarbons; however, they occasionally convert these hydrocarbons into vinyl chloride which was more toxic than the haloaliphatic hydrocarbons (Bouwer, E. J., Appl. Environ. Microbiol 45:1286-1294 (1983)).
It has been estimated that 1,2-chloroethane has an environmental half-life of approximately 50 years (Vogel, T.M., et al., Environ. Sci. Technol. 21:722-736 (1987)). The other volatile halogenated aliphatic hydrocarbons are equally as resistant. The prior art has searched for many years for a Pseudomonas strain which might be effective in degrading these halogenated hydrocarbons.